[Owncloud] help needed with encryption and corruped files

[Victor Dubiniuk]

My apologies for sending the incomplete message.

I used 4.0.2 to debug the encryption and found that the problem is in
the *OC_Crypt::decrypt
 - *it strips all 0x00 characters at the 8KB block boundary.
Please check the encryption with the attached files. One has 32 of 0x00
inside and another one is the same but has 0x05 at the 7th position.

When I change *apps/files_encryption/lib/crypt.php*  line *#136*
return rtrim($data, "\0");
to
return $data;

the file is decrypted correctly except the fact that it's last block is
padded with 0x00. (Tested on *.exe ~ 7MB)

---
Victor Dubiniuk

On Wed, Jun 13, 2012 at 6:07 PM, Victor Dubiniuk
<victor.dubiniuk at gmail.com>wrote:

> Hi all,
>
> I used 4.0.  and found that the problem is in the  *OC_Crypt::decrypt*
> it strips all 0x00 characters at the block boundary.
> Please check with the attached files.
> One has 32 of 0x00 inside and another one -
>
> When I change *apps/files_encryption/lib/crypt.php*  line *#136*
> return rtrim($data, "\0");
> to
> return $data;
>
> the file is decrypted correctly except the fact that it's last block is
> padded with 0x00.
>
> I hope that it will be helpful.
>
>
> ---
> Victor Dubiniuk
>
> On Wed, Jun 13, 2012 at 4:45 AM, Michael Gapczynski <mtgap at owncloud.com>wrote:
>
>> On Tuesday, June 12, 2012 12:52:06 PM Klaas Freitag wrote:
>> > On 04.06.2012 18:33, Klaas Freitag wrote:
>> > > On 04.06.2012 18:13, Frank Karlitschek wrote:
>> > >> Hi,
>> > >>
>> > >> we have a very evil bug report about corrupted files together with
>> the
>> > >> encryption app.
>> > >>
>> > >> http://bugs.owncloud.org/thebuggenie/owncloud/issues/oc-912
>> > >> http://forum.owncloud.org/viewtopic.php?f=3&t=2726
>> > >>
>> > >> Everything works for me and I can´t find the problem
>> > >> Can someone help me with reproducing it?
>> > >
>> > > I can reproduce it with a Firefox on Linux and on Windows 7. I have
>> > > master running from this morning.
>> >
>> > Frank, do you think that
>> > http://bugs.owncloud.org/thebuggenie/owncloud/issues/oc-669
>> > can be related to this problem? Is there a fix already for #912?
>> >
>> > Thanks,
>> >
>> > Klaas
>>
>> It seems that binary data has problems going through the encryption. I did
>> some research and read that base64_encode()/decode() should allow binary
>> files
>> to be encrypted. My attempts to encode and decode the data with base64
>> still
>> result in corrupted binary files.
>>
>> http://bytes.com/topic/php/answers/8958-binary-encryption
>>
>>
>> http://stackoverflow.com/questions/6033972/encrypting-files-with-php-mcrypt-
>> is-corrupting-docx-and-other-microsoft-office<http://stackoverflow.com/questions/6033972/encrypting-files-with-php-mcrypt-is-corrupting-docx-and-other-microsoft-office>
>>
>> http://www.itnewb.com/tutorial/PHP-Encryption-Decryption-Using-the-MCrypt-
>> Library-libmcrypt<http://www.itnewb.com/tutorial/PHP-Encryption-Decryption-Using-the-MCrypt-Library-libmcrypt>
>>
>>
>>
>> Michael
>> _______________________________________________
>> Owncloud mailing list
>> Owncloud at kde.org
>> https://mail.kde.org/mailman/listinfo/owncloud
>>
>
>
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